/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;

import java.nio.channels.FileChannel;
import sun.nio.ch.FileChannelImpl;


/**
 * A <code>FileInputStream</code> obtains input bytes
 * from a file in a file system. What files
 * are  available depends on the host environment.
 *
 * <p><code>FileInputStream</code> is meant for reading streams of raw bytes
 * such as image data. For reading streams of characters, consider using
 * <code>FileReader</code>.
 *
 * @author Arthur van Hoff
 * @see java.io.File
 * @see java.io.FileDescriptor
 * @see java.io.FileOutputStream
 * @see java.nio.file.Files#newInputStream
 * @since JDK1.0
 */
public class FileInputStream extends InputStream {

  /* File Descriptor - handle to the open file */
  private final FileDescriptor fd;

  /**
   * The path of the referenced file
   * (null if the stream is created with a file descriptor)
   */
  private final String path;

  private FileChannel channel = null;

  private final Object closeLock = new Object();
  private volatile boolean closed = false;

  /**
   * Creates a <code>FileInputStream</code> by
   * opening a connection to an actual file,
   * the file named by the path name <code>name</code>
   * in the file system.  A new <code>FileDescriptor</code>
   * object is created to represent this file
   * connection.
   * <p>
   * First, if there is a security
   * manager, its <code>checkRead</code> method
   * is called with the <code>name</code> argument
   * as its argument.
   * <p>
   * If the named file does not exist, is a directory rather than a regular
   * file, or for some other reason cannot be opened for reading then a
   * <code>FileNotFoundException</code> is thrown.
   *
   * @param name the system-dependent file name.
   * @throws FileNotFoundException if the file does not exist, is a directory rather than a regular
   * file, or for some other reason cannot be opened for reading.
   * @throws SecurityException if a security manager exists and its <code>checkRead</code> method
   * denies read access to the file.
   * @see java.lang.SecurityManager#checkRead(java.lang.String)
   */
  public FileInputStream(String name) throws FileNotFoundException {
    this(name != null ? new File(name) : null);
  }

  /**
   * Creates a <code>FileInputStream</code> by
   * opening a connection to an actual file,
   * the file named by the <code>File</code>
   * object <code>file</code> in the file system.
   * A new <code>FileDescriptor</code> object
   * is created to represent this file connection.
   * <p>
   * First, if there is a security manager,
   * its <code>checkRead</code> method  is called
   * with the path represented by the <code>file</code>
   * argument as its argument.
   * <p>
   * If the named file does not exist, is a directory rather than a regular
   * file, or for some other reason cannot be opened for reading then a
   * <code>FileNotFoundException</code> is thrown.
   *
   * @param file the file to be opened for reading.
   * @throws FileNotFoundException if the file does not exist, is a directory rather than a regular
   * file, or for some other reason cannot be opened for reading.
   * @throws SecurityException if a security manager exists and its <code>checkRead</code> method
   * denies read access to the file.
   * @see java.io.File#getPath()
   * @see java.lang.SecurityManager#checkRead(java.lang.String)
   */
  public FileInputStream(File file) throws FileNotFoundException {
    String name = (file != null ? file.getPath() : null);
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
      security.checkRead(name);
    }
    if (name == null) {
      throw new NullPointerException();
    }
    if (file.isInvalid()) {
      throw new FileNotFoundException("Invalid file path");
    }
    fd = new FileDescriptor();
    fd.attach(this);
    path = name;
    open(name);
  }

  /**
   * Creates a <code>FileInputStream</code> by using the file descriptor
   * <code>fdObj</code>, which represents an existing connection to an
   * actual file in the file system.
   * <p>
   * If there is a security manager, its <code>checkRead</code> method is
   * called with the file descriptor <code>fdObj</code> as its argument to
   * see if it's ok to read the file descriptor. If read access is denied
   * to the file descriptor a <code>SecurityException</code> is thrown.
   * <p>
   * If <code>fdObj</code> is null then a <code>NullPointerException</code>
   * is thrown.
   * <p>
   * This constructor does not throw an exception if <code>fdObj</code>
   * is {@link java.io.FileDescriptor#valid() invalid}.
   * However, if the methods are invoked on the resulting stream to attempt
   * I/O on the stream, an <code>IOException</code> is thrown.
   *
   * @param fdObj the file descriptor to be opened for reading.
   * @throws SecurityException if a security manager exists and its <code>checkRead</code> method
   * denies read access to the file descriptor.
   * @see SecurityManager#checkRead(java.io.FileDescriptor)
   */
  public FileInputStream(FileDescriptor fdObj) {
    SecurityManager security = System.getSecurityManager();
    if (fdObj == null) {
      throw new NullPointerException();
    }
    if (security != null) {
      security.checkRead(fdObj);
    }
    fd = fdObj;
    path = null;

        /*
         * FileDescriptor is being shared by streams.
         * Register this stream with FileDescriptor tracker.
         */
    fd.attach(this);
  }

  /**
   * Opens the specified file for reading.
   *
   * @param name the name of the file
   */
  private native void open0(String name) throws FileNotFoundException;

  // wrap native call to allow instrumentation

  /**
   * Opens the specified file for reading.
   *
   * @param name the name of the file
   */
  private void open(String name) throws FileNotFoundException {
    open0(name);
  }

  /**
   * Reads a byte of data from this input stream. This method blocks
   * if no input is yet available.
   *
   * @return the next byte of data, or <code>-1</code> if the end of the file is reached.
   * @throws IOException if an I/O error occurs.
   */
  public int read() throws IOException {
    return read0();
  }

  private native int read0() throws IOException;

  /**
   * Reads a subarray as a sequence of bytes.
   *
   * @param b the data to be written
   * @param off the start offset in the data
   * @param len the number of bytes that are written
   * @throws IOException If an I/O error has occurred.
   */
  private native int readBytes(byte b[], int off, int len) throws IOException;

  /**
   * Reads up to <code>b.length</code> bytes of data from this input
   * stream into an array of bytes. This method blocks until some input
   * is available.
   *
   * @param b the buffer into which the data is read.
   * @return the total number of bytes read into the buffer, or <code>-1</code> if there is no more
   * data because the end of the file has been reached.
   * @throws IOException if an I/O error occurs.
   */
  public int read(byte b[]) throws IOException {
    return readBytes(b, 0, b.length);
  }

  /**
   * Reads up to <code>len</code> bytes of data from this input stream
   * into an array of bytes. If <code>len</code> is not zero, the method
   * blocks until some input is available; otherwise, no
   * bytes are read and <code>0</code> is returned.
   *
   * @param b the buffer into which the data is read.
   * @param off the start offset in the destination array <code>b</code>
   * @param len the maximum number of bytes read.
   * @return the total number of bytes read into the buffer, or <code>-1</code> if there is no more
   * data because the end of the file has been reached.
   * @throws NullPointerException If <code>b</code> is <code>null</code>.
   * @throws IndexOutOfBoundsException If <code>off</code> is negative, <code>len</code> is
   * negative, or <code>len</code> is greater than <code>b.length - off</code>
   * @throws IOException if an I/O error occurs.
   */
  public int read(byte b[], int off, int len) throws IOException {
    return readBytes(b, off, len);
  }

  /**
   * Skips over and discards <code>n</code> bytes of data from the
   * input stream.
   *
   * <p>The <code>skip</code> method may, for a variety of
   * reasons, end up skipping over some smaller number of bytes,
   * possibly <code>0</code>. If <code>n</code> is negative, the method
   * will try to skip backwards. In case the backing file does not support
   * backward skip at its current position, an <code>IOException</code> is
   * thrown. The actual number of bytes skipped is returned. If it skips
   * forwards, it returns a positive value. If it skips backwards, it
   * returns a negative value.
   *
   * <p>This method may skip more bytes than what are remaining in the
   * backing file. This produces no exception and the number of bytes skipped
   * may include some number of bytes that were beyond the EOF of the
   * backing file. Attempting to read from the stream after skipping past
   * the end will result in -1 indicating the end of the file.
   *
   * @param n the number of bytes to be skipped.
   * @return the actual number of bytes skipped.
   * @throws IOException if n is negative, if the stream does not support seek, or if an I/O error
   * occurs.
   */
  public native long skip(long n) throws IOException;

  /**
   * Returns an estimate of the number of remaining bytes that can be read (or
   * skipped over) from this input stream without blocking by the next
   * invocation of a method for this input stream. Returns 0 when the file
   * position is beyond EOF. The next invocation might be the same thread
   * or another thread. A single read or skip of this many bytes will not
   * block, but may read or skip fewer bytes.
   *
   * <p> In some cases, a non-blocking read (or skip) may appear to be
   * blocked when it is merely slow, for example when reading large
   * files over slow networks.
   *
   * @return an estimate of the number of remaining bytes that can be read (or skipped over) from
   * this input stream without blocking.
   * @throws IOException if this file input stream has been closed by calling {@code close} or an
   * I/O error occurs.
   */
  public native int available() throws IOException;

  /**
   * Closes this file input stream and releases any system resources
   * associated with the stream.
   *
   * <p> If this stream has an associated channel then the channel is closed
   * as well.
   *
   * @throws IOException if an I/O error occurs.
   * @revised 1.4
   * @spec JSR-51
   */
  public void close() throws IOException {
    synchronized (closeLock) {
      if (closed) {
        return;
      }
      closed = true;
    }
    if (channel != null) {
      channel.close();
    }

    fd.closeAll(new Closeable() {
      public void close() throws IOException {
        close0();
      }
    });
  }

  /**
   * Returns the <code>FileDescriptor</code>
   * object  that represents the connection to
   * the actual file in the file system being
   * used by this <code>FileInputStream</code>.
   *
   * @return the file descriptor object associated with this stream.
   * @throws IOException if an I/O error occurs.
   * @see java.io.FileDescriptor
   */
  public final FileDescriptor getFD() throws IOException {
    if (fd != null) {
      return fd;
    }
    throw new IOException();
  }

  /**
   * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
   * object associated with this file input stream.
   *
   * <p> The initial {@link java.nio.channels.FileChannel#position()
   * position} of the returned channel will be equal to the
   * number of bytes read from the file so far.  Reading bytes from this
   * stream will increment the channel's position.  Changing the channel's
   * position, either explicitly or by reading, will change this stream's
   * file position.
   *
   * @return the file channel associated with this file input stream
   * @spec JSR-51
   * @since 1.4
   */
  public FileChannel getChannel() {
    synchronized (this) {
      if (channel == null) {
        channel = FileChannelImpl.open(fd, path, true, false, this);
      }
      return channel;
    }
  }

  private static native void initIDs();

  private native void close0() throws IOException;

  static {
    initIDs();
  }

  /**
   * Ensures that the <code>close</code> method of this file input stream is
   * called when there are no more references to it.
   *
   * @throws IOException if an I/O error occurs.
   * @see java.io.FileInputStream#close()
   */
  protected void finalize() throws IOException {
    if ((fd != null) && (fd != FileDescriptor.in)) {
            /* if fd is shared, the references in FileDescriptor
             * will ensure that finalizer is only called when
             * safe to do so. All references using the fd have
             * become unreachable. We can call close()
             */
      close();
    }
  }
}
